The Majestic Squire uses a standard 3/8" tube. PSI does not offer a pre-cut "extra tube" for this kit. Pick up some 3/8" tubing and cut it to lenght. I have the lenght in my shop notes if you do not have it. I'll also look to see if I have any extra tubes cut for them if you need.
When I find a kit that I like such as the Majestic Squire, I always buy a set of extra tubes or cut some from stock for the occasional unexpected oooooops. Plus it can give me a head start if I don't have a kit in stock.